This invention relates to power transmissions and, more particularly, to power transmissions having three planetary gearsets and six torque-transmitting mechanisms in order to provide at least seven forward speed ratios and one reverse speed ratio.
Automatic shifting power transmissions are currently used in a majority of the vehicles produced in the United States. These vehicles generally employ three- and four-speed power transmissions. More recently, a trend towards more ratios, such as five- and six-speed power transmissions, has been proposed. In fact, some manufacturers do provide five-speed transmissions. Many of the vehicles utilizing manual type transmissions or countershaft type transmissions employ five- and six-speed power transmissions.
The five- and six-speed power transmissions provide improved vehicle acceleration performance and fuel economy when compared with three- and four-speed transmissions. Seven-speed transmissions offer further vehicle acceleration performance and fuel economy improvements over five- and six-speed power transmissions. However, seven-speed power transmissions have not been proposed due to the complexity of these assemblies, as well as size and cost. There are many current patents that describe five- and six-speed power transmissions. Some of the six-speed power transmission patents, especially those assigned to the assignee of the present invention, describe six-speed power transmissions in families, wherein one or more family members incorporate a seven-speed power transmission.
It is an object of the present invention to provide an improved family of seven-speed power transmissions incorporating three planetary gearsets and six torque-transmitting mechanisms.
In one aspect of the present invention, the six torque-transmitting mechanisms are engaged in combinations of two to establish at least seven forward speed ratios and one reverse speed ratio within the planetary gearsets.
In another aspect of the present invention, an interconnecting member continuously interconnects a first member of the first planetary gearset and a first member of the second planetary gearset.
In still another aspect of the present invention, a second interconnecting member continuously interconnects a second member of the first planetary gearset with a first member of the third planetary gearset.
In yet another aspect of the present invention, a third interconnecting member continuously interconnects a second member of the second planetary gearset with a second member of the third planetary gearset.
In yet still another aspect of the present invention, a third member of the first planetary gearset is continuously interconnected with a stationary member, such as a transmission case or housing.
In a yet still another aspect of the present invention, an output shaft is continuously interconnected with at least one member of one of the planetary gearsets.
In yet still another aspect of the present invention an input shaft is not continuously connected with any of the planetary gear sets but rather only selectively connectible therewith through selectively engageable torque transmitting mechanisms.
In a further aspect of the present invention, a first of the torque-transmitting mechanisms selectively interconnects an input shaft with a member of one of the planetary gearsets.
In a still further aspect of the present invention, a second of the torque-transmitting mechanisms selectively interconnects the input shaft with a member of one of the planetary gearsets not interconnected with the first torque-transmitting mechanism.
In yet a further aspect of the present invention, a third of the torque-transmitting mechanisms selectively interconnects a member of one of the-planetary gearsets or one of the interconnecting members with either the input shaft, the output shaft, or another member of one of the planetary gearsets.
In a yet still further aspect of the present invention, a fourth of the torque-transmitting mechanisms selectively interconnects a member of one of the planetary gearsets with either the input shaft, the output shaft, or another member of one of the planetary gearsets.
In a still further aspect of the present invention, a fifth of the torque-transmitting mechanisms selectively interconnects at least one member of one of the planetary gearsets with another member of the first, second, or third planetary gearset, or with the transmission housing.
In a further aspect of the present invention, a sixth of the torque-transmitting mechanisms selectively interconnects a member of one of the planetary gearsets with either the output shaft, another member of one of the planetary gearsets, or with the transmission housing.
In a yet further aspect of the present invention, each of the members of the planetary gearsets can be either a sun gear member, a ring gear member, or a planet carrier assembly member, and each of the planet carrier assembly members can be either of the single pinion type or of the double pinion type.